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Wireless Sensor Networks Able to Self-Organize
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Imagine a building that can monitor itself to save energy or a ring with an embedded biomedical sensor that can be worn to monitor the vital signs of nursing home residents. These are a couple of the applications for emerging wireless networks of tiny, low-power sensors that can organize themselves.
Such networks already are having standards created for them by an international alliance called ZigBee, which has more than 100 member organizations and companies such as the Korea Electronics Research Institute, Samsung Electronics Ltd and Mitsubishi Electric Corp. An early version of the ZigBee specification was expected at the end of 2004.
Some companies and university labs, including the Massachusetts Institute of Technology's (MIT) Media Lab and The University of California at Berkeley Intel Berkeley Research Lab, already have demonstrated earlier experimental self-organizing wireless sensor networks.
The US so far has led in developing the wireless sensor networking technology components, including hardware and software. One reason is because the origins of the idea were at the US Defense Advanced Research Project Agency (DARPA), which was envisioning among other things mesh networks of sensors which could be thrown over a battlefield to communicate the environment and safety of the area to a satellite before soldiers advanced onto the field. DARPA originally hoped such networks could last a couple weeks, but they now are envisioned for use in industrial, medical and consumer applications for months and even years, said Sokwoo Rhee, chief technology officer for Millenial Net Inc, a US wireless sensor network elements company spun out from MIT. Its component products work atop ZigBee.
"The US and Europe are deploying this technology faster than other countries [and regions], said Rhee. "Korea and Japan also are active. And China is about five years away from wireless sensor networks. Rhee said that while building automation likely will be the first big market, such sensor networks also could be used in supply-chain management, automatic meter reading, security and other low-data-rate applications.
i-Beans
Millennial, which was founded in 2000, makes a component for OEM customers that could include building management system companies such as Honeywell Inc, Siemens AG, and Invensys Building Systems Inc. Millennial's i-Bean sensor is about the size of a postage stamp, and includes software, an RF transceiver and a processor. The company's products can be used to build a scalable, low power, star-mesh wireless network by combining sensor interface endpoints and routers with a gateway.
One challenge Millennial faced was getting a small and low-power energy source. Rhee said the product can run on a simple, off-the-shelf, CR2032 lithium calculator battery for 5-10 years. In standby mode, the i-Bean consumes about 12mA. If the sensor needs to talk to a network once per 100 seconds, a small battery will last about 1.4 years, but a larger lithium cell can be used for 6.5 years. i-Beans were able to achieve lower power consumption than most other similar networks in development because Millennial's protocol does not use polling. The i-Bean is only turned on when it has data to transmit or when it checks for the presence of routers.
Bluetooth uses frequency-hopping spread spectrum (FHSS), so that a node trying to enter the network at power-up must first search through many frequencies to locate which one it should use. Millennial, by comparison, is focused on low-data-rate applications that need long battery life. Millennial uses narrowband or direct-sequence spread-spectrum (DSSS) technologies so the network can be reconfigured more quickly as devices enter or exit it.
The i-Bean components conform to the emerging IEEE 802.15.4 standard for low-power, personal-area networks. The standard will specify DSSS radios in three bands: 868MHz, 915MHz, and 2.4GHz. A typical i-Bean network could run from about 115kbps to 250kbps with the sensors in an area up to about 30 meters (100 ft).
The Millennial products can configure themselves into a mesh network. The endpoints connect directly to analog or digital sensors and actuators. The elements of the network self-organize at power-up, and reconfigure themselves if there are changes in the environment, network traffic and device status or location. The sensors can fit just about anywhere, including within an electrical outlet in a wall.
by Lori Valigra
(January 2005 Issue, Nikkei Electronics Asia)
Such networks already are having standards created for them by an international alliance called ZigBee, which has more than 100 member organizations and companies such as the Korea Electronics Research Institute, Samsung Electronics Ltd and Mitsubishi Electric Corp. An early version of the ZigBee specification was expected at the end of 2004.
Some companies and university labs, including the Massachusetts Institute of Technology's (MIT) Media Lab and The University of California at Berkeley Intel Berkeley Research Lab, already have demonstrated earlier experimental self-organizing wireless sensor networks.
The US so far has led in developing the wireless sensor networking technology components, including hardware and software. One reason is because the origins of the idea were at the US Defense Advanced Research Project Agency (DARPA), which was envisioning among other things mesh networks of sensors which could be thrown over a battlefield to communicate the environment and safety of the area to a satellite before soldiers advanced onto the field. DARPA originally hoped such networks could last a couple weeks, but they now are envisioned for use in industrial, medical and consumer applications for months and even years, said Sokwoo Rhee, chief technology officer for Millenial Net Inc, a US wireless sensor network elements company spun out from MIT. Its component products work atop ZigBee.
"The US and Europe are deploying this technology faster than other countries [and regions], said Rhee. "Korea and Japan also are active. And China is about five years away from wireless sensor networks. Rhee said that while building automation likely will be the first big market, such sensor networks also could be used in supply-chain management, automatic meter reading, security and other low-data-rate applications.
i-Beans
Millennial, which was founded in 2000, makes a component for OEM customers that could include building management system companies such as Honeywell Inc, Siemens AG, and Invensys Building Systems Inc. Millennial's i-Bean sensor is about the size of a postage stamp, and includes software, an RF transceiver and a processor. The company's products can be used to build a scalable, low power, star-mesh wireless network by combining sensor interface endpoints and routers with a gateway.
One challenge Millennial faced was getting a small and low-power energy source. Rhee said the product can run on a simple, off-the-shelf, CR2032 lithium calculator battery for 5-10 years. In standby mode, the i-Bean consumes about 12mA. If the sensor needs to talk to a network once per 100 seconds, a small battery will last about 1.4 years, but a larger lithium cell can be used for 6.5 years. i-Beans were able to achieve lower power consumption than most other similar networks in development because Millennial's protocol does not use polling. The i-Bean is only turned on when it has data to transmit or when it checks for the presence of routers.
Bluetooth uses frequency-hopping spread spectrum (FHSS), so that a node trying to enter the network at power-up must first search through many frequencies to locate which one it should use. Millennial, by comparison, is focused on low-data-rate applications that need long battery life. Millennial uses narrowband or direct-sequence spread-spectrum (DSSS) technologies so the network can be reconfigured more quickly as devices enter or exit it.
The i-Bean components conform to the emerging IEEE 802.15.4 standard for low-power, personal-area networks. The standard will specify DSSS radios in three bands: 868MHz, 915MHz, and 2.4GHz. A typical i-Bean network could run from about 115kbps to 250kbps with the sensors in an area up to about 30 meters (100 ft).
The Millennial products can configure themselves into a mesh network. The endpoints connect directly to analog or digital sensors and actuators. The elements of the network self-organize at power-up, and reconfigure themselves if there are changes in the environment, network traffic and device status or location. The sensors can fit just about anywhere, including within an electrical outlet in a wall.
by Lori Valigra
(January 2005 Issue, Nikkei Electronics Asia)
